Method and apparatus for slowing the forward speed of a towed submerged vessel



114-253. XR 3,296,996 SR an. 10, 1967 w. J. MILLER 3,296,996 METHOD ANDAPPARATUS FOR SLOWING THE FORWARD SPEED 1 OF A TOWED SUBMERGED VESSELFiled March 24, 1965 2 Sheets-Sheet 1 ELLE-r4 Tia-5 A TI'OP/VEY Jan. 10,1967 w. J. MILLER 3,296,996

METHOD AND APPARATUS FOR SLOWING-THE FORWARD SPEED OF A TDWED SUBMERGEDVESSEL Filed March 24, 1965 2 Sheets-Shet 2 fits- E INVENTOR. W/LL /'A Md. 1L4/L4 E-Q A TTOQA/EY 3,296,996 PatentedJan. 10, 1987 3,296 996 5METHOD AND APPARATUS FOR SLOWING THE FORWARD SPEED OF A TOWED SUBMERGEDVESSEL William J. Miller, Ponca City, Okla, assignor to Contimay occur,or that the tow line may become fouled in nental Oil Company, PoacaCity, Okla., a corporation of Delaware F lied Mar. 24, 1965, Ser. No.442,285

25 Claims. (Cl. 114-235) invention relates to amethod for deceleratingva subspeed by'fa towirig slung: it has previously been proposed toprovide cargo carrying submersibles which can be moved by a towingvessel 7 through relatively deep bodies of water at relatively highspeeds while submerged. Transport of cargoes such as crude oil and otherliquids by this method presents a number of advantages over surfacetransport. These advantages may be generally summarized as therelatively great improvement in the economy of locomotion of the cargocarrying vessel which is achieved, the reduction in manpowerrequirements for servicing the towed vessel and maintaining it on acorrect course during the tow, and, lastly, a saving in maintenance costof the towed cargo vessel as a result of the avoidance of structuraldeterioration which normally results in surface cargo vessels due tosubjection of the vessel to wave action and high winds which areencountered during surface towing.

With the recent development of a submersible which can be towed at apredetermined depth in the water at relatively high speeds with a highdegree of control of buoyancy and depth, large cargoes of crude oil orother liquids can be towed over substantial distances at a fraction ofthe cost which would be entailed in moving the same cargo by surfacetransport. One successful recent development permits the submersiblebarge to be towed at a depth of from 10 to 40 meters at speeds up to14.5 knots while carrying a cargo of at least 5,000 tons of crude oil.The drag imposed upon the towing vessel has been reduced to the extentthat, at speeds of about 15 knots, only about 1 knot of speed is lost bythe towing vessel as a result of the submerged tow.

The development of a submerged barge which encounters a minimum ofresistance to its forward movement as a result of hydrodynamic forcesgives rise to a serious problem which must be overcome before the bargecan be safely towed at relatively high speeds. Concisely stated, thisproblem is that of rapidly decelerating the tow at any time whencontinued forward movement of the tow will ultimately present a hazardto the towing vessel, or to any object forward of the tow in its line ofmovement. sirability of being able to quickly decelerate the tow undercircumstances where a decrease in tension on the tow lineinterconnecting the tow to the towing vessel is likely to result in themovement of the submerged vessel through the water becoming erratic, andparticularly, where the submerged vessel is characterized in havinghydrodynamic characteristics which will permit it to dive when tensionis decreased in the tow line.

A condition sometimes requiring rapid deceleration of the submerg dvessel will be that occurring when the towing vessel finds it necessaryto come to an emergency stop, or to back down full in order to rapidlyreduce the way on the towing vessel. In this situation, it will beapparent that the submerged vessel, unless braked or decelerated in somemanner, will quickly overtake the towing vessel with the result that adisastrous collision Another aspect of this problem is the de-' thescrews of the towing vessel. In a recent design of submersible barge, areduction in the tension of the tow cable which may result from anemergency stop on'the part of the towing vessel can also permit thebarge to rapidly dive to an excessive depth as the result ofthe'inclination of diving planes provided on the barge. This situationmay cause the hull of the submersible barge to be ruptured by excessivehydrostatic pressure. or. in one barge design, may require theemployment of emergency pressure sensitive equipment to blow reserveballast cartied by the barge. thereby causing it to rise to the surface.Difficulties of reballasting the barge are then presented. which in somedesigns, cannot be overcome while underway or adrift in the high seas,but can be effected only by returning to port.

Another situation which may make it highly desirable to rapidlydecelerate the tow is that which may be experienccd where the towingship must necessarily undergo an emergency turn. In this. situation, theturning radius which can be achieved by the towing vessel may beconsiderably smaller than the turning radius of the towed submersiblewith the result that the submersible swings through a wider arc than thetowing vessel and may collide with any objects outside the turningradius of the towing vessel unless in some manner decelerated.

Under any of the described'conditions making it clesirable to rapidlydecelerate or brake the submerged barge, reliance upon devices carriedby. or located within. the towed vessel for accomplishing suchdeceleration presents certain disadvantages. The use of sea anchors orother devices carried on the tow and actuated by an electrical circuitconnected between the towing vessel and the tow. or any similar type ofdevice actuated from the tow. would, in most instances, require that thetow be stopped and brought to the surface in order to reset the brakingdevice and prevent it from retarding the normal movement of the towthrough the water following the emergency. Alternatively, if it werenecessary to reach the braking device or the connections thereto duringthe towing omrations and without surfacing the tow. a diver would berequired and special tools for underwater work would be necessary.Extending electrical circuitry or other actuating means between thetowing vessel and the tow also presents certain technical difficulties.

The present invention comprises a method and apparatus for deceleratinga submerged towed vessel, which device can be actuated and controlledfrom the towing vessel and which can be returned to an inactivatedstatus immediately after the submerged vessel has been decelerated tothe extent desired. Inactivation of the braking apparatus can beaccomplished without access to the towed vessel, and therefore withoutthe requirement that the towed vessel be brought to the surface. Theapparatus employed in the invention to accomplish deceleration does notprovide any interference with the forward movement of the towing vesselby the submerged towed vessel during normal operation when the device isinactivated. Moreover, the braking device can be made compact in size tofacilitate storage at times when it is not in use, and is relativelysimple and inexpensive in construction.

Broadly described, the brakin devii used in practicing the method of thepresent invention comprises means for resisting fluid flow slidablymounted on the tow line interconnecting the towing vessel with thesubmerged flow resisting means along the luw line, said control meansbeing connected to and operable from the towing vessel. Most embodimentsof the bnking device also include shock absorbing means disposed alongthe tow line between the fiuid flow resistance means and the towedvessel for cushioning the impact of the towed vessel with the resistancemeans. In a preferred embodiment of the invention, the means forresisting fluid flow comprises an annular body slidably surrounding thetow line and a plurality of elongated hydrodynamic resistance finsextending radially from the body for'opposing fluid flow .thereby in thedirection of the towed vessel. 2

It should be pointed out that the fluid flow resistance meansaccomplishes its braking or decelerating action by the resistance whichit ofifers to the flow of water past the device, and also by thecreation of a turbulent condition around the hull of the submerged tow,imposing a drag thereon, and interfering with the hydromaticstreamlining of the tow so as to cause it to encounter more resistanceto continued forward movement through the water. The method of theinvention can thus be summarized as moving on the tow line whichinterconnects the submerged tow and the towing vessel, a turbulencegenerating and fluid flow resistance device which offers greaterresistance to the flow of water thereby than does the submerged vessel,such movement of the device being from a position on the tow line whichis above the water and adjacent the towing vessel to a position in thewater and closer to the submerged vessel.

As the turbulence generating and fluid flow resistance device is movedto this position in the water, the towing vessel continues to move awayfrom the device and to simultaneously pull the tow line through theturbulence generating and fluid flow resistance device so that thesubmerged tow converges on the device until the device is contactedthereby. Continued forward movement of the submerged tow and the fluidflow resistance device is then opposed by the turbulence generated bythe device and the resistance offered by the device to fluid flowthereby until the submerged tow has been decelerated to the desiredextent. As the final step in the process, the turbulence generating andfluid flow resistance device can be returned to its original position bymovement along the tow line, using movement control means actuated fromthe towing vessel.

From the foregoinng description of the invention, it will have becomeapparent that it is a major objective of the present invention toprovide aiwmparatus for de- An additional object of the presentinvention is 5 56 vide a device for decelerating a submerged tow, whichdevice is continuously within the control of the towing vessel, is notcarried by, or directly connected to, the submerged tow at any timeduring its use, and can be returned to an inactivated status without thenece ssit oi Restor ng rn q ch so a d h E T- An additional object of thepresent invention is to provide apparatus for decelerating a submergedtow, which apparatus is relatively simple and inexpensive inconstruction, and can be utilized successfully a plurality of timeswithout mechanical failure.

In addition to the foregoing objects and advantages, additional objectsand desirable features of the present invention will become apparent asthe following detailed description of the invention is read inconjunction with the accompanying drawings which illustrate theinvention.

In the drawings:

FIGURE 1 is a somewhat schematic illustration of the environment of theuse of the present invention, and depicts a submerged barge being towedastern of a towing vessel by means of an interconnecting tow cable whichcarries one embodiment of the decelerating device of the presentinvention.

FIGURE 2 is an enlarged perspective view of the embodimcnt of thedecelerating device schematically illustrated in FIGURE 1.

FIGURE 3 is a view in section taken through the longitudinal axis of thedecelerating device shown in FIGURE 2 and illustrating various detailsof construction of the device.

FIGURE 4 is a view in elevation of a modified embodiment ofthedecelerating device of the invention.

FIGURE Sis a view in elevation of another modification of thedecelerating device of the invention.

FIGURE 6 is a detail sectional view illustrating a particular'structurewhich may be used in combination with the movable elements of thedecelerating device of the invention for cushioning the impact of thedecelerating device With the towed vessel during the practice of themethod of the invention.

Referring now to the drawings in detail, and particulariy to FIGURE 1, asubmerged tow, such as a submersible barge 10, is connected by aflexible tow line 12 to the stern of a towing vessel 14. The barge 10 isa streamlined, hydrodynamically stable craft which is specially designedfor underwater movement, and which contains suitable compartmentation(not shown) for the transport of crude oil or other liquids. The towline 12 is preferably a suitable multi-stranded steel cable of from 1 to3 inches in diameter, and in normal towing situations may be streamedfrom the towing vessel 14 so that a length of from 300' to 1,500 feet ofcable extends between the towing vessel 14 and the tow 10. A suitablecapstan or winch 16 is positioned on the stern or fantail of the towingvessel 14, and one end of the tow line 12 is reeled thereon so that theline can be paid out or retrieved by the winch. Preferably, an automatictensioning device (not shown) is associated with the winch 16 formaintaining a relatively constant tension in the tow line 12 forpurposes hereinafter described.

Under normal towingconditions, the decelerating device 18 of the presentinvention is movably mounted on the tow line 12 in a position which isabove the water and relatively close to the stern of the towing ship 14.The decelerating device 18 is retained in this position by a returncable 20 which extends through suitable checks in the fantail of thevessel 12 to a small capstan or winch 22. The winch 22 is free runningin one direction so that little or no resistance is offered to thepaying out of the return cable 20 when a brake (not shown) is releasedto permit the decelerating device 18 to move down the tow line 12 towardthe tow 10. It is further highly desirable that the brake release (notshown) of the return cable 20, and also the motor and clutch (not shown)for driving the winch 22 in a direction to return the deceleratingdevice 18 to the position illustrated in FIGURE 1 include remote controlelectrical or hydraulic circuitry to permit this apparatus to beoperated from the bridge of a towing vessel 14.

The details of construction of one embodiment of the decelerating deviceof the invention are best illustrated in FIGURES 2 and 3. The deviceincludes an annular body which may suitably take the form of a sleeve 24dimensioned to slidably encircle the tow line 12. The sleeve 24 ispreferably provided with a plurality of friction reducing elements, suchas wheels or rollers 26, rotatably mounted in the sleeve 24 at each endthereof and projecting radially inwardly from the sleeve to bear againstthe tow line 12.

At its end closest to the tow 10, the sleeve 24 is connected to andsupports a shock absorbing device designated generally by referencecharacter 28 which includes an annular flange 39 secured to the sleeve24, a plurality of piston elements 32 extending from the flange 30axially along, and spaced outwardly from, the sleeve 24, and a pluralityof apertured cylinder 34- which function conjunctively with the pistonsprovide a dashpot action in the shock absorber 28. The cylinder: 3! aresecured to' a base plate 36 which encircles, and is bonded to, anelastomeric annular cushion 38 which projects axially along the tow line12 from the retainer flange 36. The

annular cushion 38 is carried by anapnular ring 40 which loosely andslidably encircles the tow line 12. A helical' Slidably mounted on thesleeve 24 is a turbulence generating, fluid flow resistance meansdesignated generally by reference character 44. The turbulencegenerating, fluid flow resistancemeans 44 includes an annular resistancefin collar 46 which slidably surrounds the sleeve 24 and is axiallymovable therealong, and an annular retrieving ring 48 which ispositioned on the towing vessel side of the sleeve 24 from the fincollar 46. The retrieving ring 48 is dimensioned to loosely encircle thesleeve 24, and in FIGURE 3, is shown in contact with a bumper ring 50fins 52 is connected by a rigid brace 54 to the retrieving ring 48. Theopposite ends of each brace 54 are pivotally connected to the respectiveresistance fin 52 and a lug 56 on the retrieving ring 48 so that as thedistance separating the fin collar 46 from the retrieving ring 48 isvaried, the rigid resistance fins 52 are pivoted about their points ofpivotal connection to the fin collar 46. Thus, the rigid resistance fins52 may be pivoted from a flared or expanded, radially extending positionas illustrated in FIG- URE 2, to a collapsed, compact position asillustrated in FIGURE 1. Preferably, in collapsing the resistance fins52 to the inactive status illustrated in FIGURE 1, the fins are movedinwardly toward the sleeve 24 to a position such that each of the finsdefine an angle of less than 45 with the axis of the sleeve. Mostpreferably, the fins 52 are moved into near parallelism with the axis ofthe sleeve 24. In order to prevent the resistance fins 52 fromoverriding their radially expanded positions under the influence ofwater pressure, the bumper ring 50 is positioned to prevent theretrieving ring 48 from moving too far along the sleeve 24.

A plurality of flexible members 60 interconnect adjacent resistancefins52 at points relatively close to the outer or free ends of the fins..The flexible members 60, which may conveniently be chains, arepreferably slightly shorter in length than the distance between the twopoints on the adjacent fins which each of them interconnects, as suchdistance would exist at a time when the fins are ,moved into a trulyradial position relativeto the fin collar 46 or, stated differently, "toa position in which they extend at precisely 90 from the axis of thesleeve 24. Thus, in addition to their major function as turbulencegenerating and fluid flow. resistance elements, the chains 60 also limitthe pivotal movement of the resistance fins 52 to an angle of slightlyless than 90 and prevent the fins from being forced by hydrostaticpressure to a position beyond their preferred radial arrangementillustrated in FIGURE 2. The chains 60 also prevent lateral bending ofthe fins 52 under hydrodynamic pressure.

Positioned between the lugs 56 on the retrieving ring 48 is at least onereturn cable pad eye 64. Preferably, a pair of the return cable pad eyes64 are located on opposite sides of the retrieving ring 48, and areconnected to the ends of two branches of the return cable 20. The otherend of the return cable is, as previously indicated, connected to thereturn cable winch 22 located on the stern of the towing vessel 14.

A modified embodiment of the decelerating device of the invention isillustrated in FIGURE 4. In this form of the invention, the turbulencegenerating and fluid flow resistance means 44 takes the form of anannular propeller hub 68 which is rotatably mounted on the sleeve 24 bymeans of suitable bearings (not shown). At least two propeller blades 72extend radially outwardly from the hub 68 and are pitched to assure thata rapidly rotating movement will be imparted to the blades 72 and hub 68I by hydrostatic pressure exerted on the faces of the prope'ller blades.A bearing 74 is provided between the hub 68 and the flange 30 of theshock absorbing device 28 to prevent frictional drag on the hub as aresult of its contact with the shock absorbing device. In the FIGURE 4embodiment of the invention, the pad eyes employed for connecting thereturn cable 20 to the decelerating de'- vice are secured to the sleeve24 adjacent the forward end thereof and are designated by referencecharacter 76.

Yet another embodiment of the invention is illustrated in FIGURE 5 ofthe drawings. In'this construction pad eyes 76 have again been providedat the forward end of the sleeve 24 for connection to the return cable20. The turbulence generating and fluid flow resistance means, howeyer,takes the form of a plurality of cup-shaped turbulence ijeneratingelements 78 which are connected by flexible lines 80 to lugs 82 securedin circumferentially spaced relation to each other around the sleeve 24.In a preferred construction of this embodiment of the invention, the tarbulence generating elements 78 each comprises a drogue which deflectsthe water outwardly as it passes over the external surface-thereof andthus creates a substantial turbulence in the wake of the drogue and overthe skin of the tow, as well as offering substantial resistance to theflow of water past the drogue. The lengths. of the flexible lines 80interconnecting the cup-shaped turbulence generating elements 78 withtheir respective lugs 82 is such that in the operation of thedecelerating device as hereinafter described, the elements 78 can bestreamed by their lines 80 a sufiicient distance to the rear of the deticing the method of the present invention is deserving ofconsideration. This element is shown in FIGURE 6 of the drawings, andcomprises a bumper 84 of elastic material which is secured immediatelyadjacent the end of the tow line 12 which is connected, or made fast, tothe bow of the tow 10. The bumper 84 may be constructed of rubber or anyother suitable elastomer having a high degree of elasticity andcorrosion resistant characteristics. As an alternative construction tothat depicted in FIGURE 6, the elastic bumper 84 may be fixed to the bowof the barge 10 and configured so that the tow line 12 may be passedthrough the center of the mass of the elastomer and attached to the bowof the barge.

Operation The declerating device of the invention is used when the tow10 is connected through the tow line 12 to the towing vessel 14 in themanner illustrated in FIGURE 1. At this time, the towing vessel 14 andtow 10 both have way on and the towing vessel may frequently be cruisingat a relatively high speed such as, for example, about 14 to 16 knots.In this situation, the decelerating device 18 is retained by the returncable 20 in the position illustrated in FIGURE I, that is, relativelyclose to the stern of the towing vessel 14 and above the water. It willbe noted that in the case of the embodiment of the decelerating device18 which is illustrated in FIGURE 2, the resistance fins 52 are in theircollapsed status and lie generally along the axis of the sleeve 24. Thiscondition is brought about by the pullof the return cable 20 on theretrieving ring 48, a

At any time that it becomes desirable or necessary to rapidly brake ordecelerate the movement of the tow 10 through the water, the returncable 20 is released to run freely from the winch 22. This permits thedecelerating device 13 to slide down if" line 12 into the water.

.2 -During this movement of the lerating device 18, the

tension in the tow line 12 is maintained relatively constant by theconstant tensioiting device associated with the winch 16, despitevariations in the distance between the tow l0 and the towing vessel 14.

when the decelerating device 18 moves into the water in its movementalong the tow line 12, the movement of the water relative to thedecelerating device actuates the turbulence producing-fluid llowresistance elements. In the cas of the embodiment of the deceleratingdevice illustrntzxin FIGURES 2 and 3, this hydrodynamic actua lionconsi. ts of flaring or expanding the resistance fins 52 to theillustrated position.

. in FIGURE 4 of the drawings, the propeller blades 72 it soon comes torest therein and the relative movement of the towing vessel 14, tow line12 and tow 10 relative to the decelerating device is such that the towline 12 continues to move through the decelerating device in thedirection of the towing vessel and thetow 10 rapidly approaches thedecelerating device. The towing vessel 14 meanwhile continues to moveaway from the decelerating device so that the net effect may beconsidered to be a relative movement of the decelerating device down thetow line 12 to the tow 10. It will be perceived that the tow 10 willmove through the distance to the decelerating device 18 at a speedsubstantially equivalent to the velocity of the water past the tow.

When the tow 10 contacts the decelerating device 13, a considerableimpact results, and a portion of the energy lost in the impact isabsorbed in the shock absorbing device 28 so that the deceleratingdevice is not damaged.

With the decelerating device 18 hearing against the bow of the tow 10,both the tow and decelerating device continue to move forward throughthe water at the same speed. The decelerating device 18, however, olferssubstantial resistance to the flow of water thereby, and additionally,creates a substantial turbulence in the water which creates a drag onthe hull of the tow 1 0. The combined flowresistance and turbulenceeffects of the decelerating device cause the tow 10 to slow its forwardmotion to an extent such that a collision with the towing vessel 14 canbe avoided and, in cases where no means is provided for maintainingconstant tension in the tow line 12, fouling of the screws of the towingvessel by the tow line is avoided.

It will be apparent that one of the most useful applications of thedecelerating device 18 is in permitting the tow 10 to be safelycontrolled in its movements at such time as it may become necessary tomake an emergency stop or turn with the towing vessel 14. In such asituation, where the system is constructed for remote control from thebridge of the towing vessel, the captain of the towing vessel canrelease the return cable 20 from the bridge at the same instant that thecommand to reverse engines is given to the engine room. Since itnormally will take several seconds for the screws to be reversed, andseveral additional seconds for the effect of such reversal to be felt onthe towing vessel 14, the decelerating device 18 will normally be wellon its way to the tow 10 before any substantial deceleration of thetowing vessel 14 occurs.

The decelerating effects obtainable by the use of the severalembodiments of the decelerating device 18 illustrated in theaccompanying drawings are generally similar. The understanding of theinvention may be further enhanced, however, by briefly describing themanner in which each achieves such decelerating-effects. In the case ofthe embodiment illustrated in FlGURES 2 and 3, the radially extendingresistance fins 52 resist flow of the water thereby and result in agradually increasing braking force. The second action of the resistancefins 52 is to set up a turbulent condition behind the fins which causesa corresponding increase in the skin resistance of the tow 10. The towis thereby caused to slow its forward speed.

and hub 74 are caused to rotate rapidly upon the sleeve 24 by thehydrostatic pressure of the passing water. The propeller thus causesactually less drag due to frictional resistance to thepassage of waterthan it would were it not permitted to rotate on the sleeve 24. Theturbulence which is created by the rapidly rotating propeller is,however, the primary decelerating effect attributable to this embodimentof the invention, and this turbulence causes a considerable brakingaction due to its friction and drag upon the skin of the tow 10. Thebraking effect achieved is graduated in that as the tow commences toslow, the speed at which the propeller blades 72 are rotated isdecreased, and thus the amount of turbulence generated by the propellerassembly is also decreased.

The drogue arrangement illustrated in FIGURE 5 of the drawings dependsupon both the frictional resistance to the passage of the waterdeveloped by the drogues 78 and also upon the turbulence which iscreated by the drogues as they pass through the water. The drogues arestreamed along the tow 10 on all sides thereof so that the turbulencecreated by the drogues acts over substantially the entire surface areaof the tow.

In addition, it should be noted that when the drogues are slowed to apredetermined speed they surface and are further slowed by wave actionat the waters surface. Moreover, once the tow ship is under way thebraking device can be hauled in to the towing ship and used again whennecessity demands, either automatically or manually.

From the foregoing description of the invention. it will be perceivedthat the present invention provides a novel and highly effectiveapparatus for decelerating or braking a towed vessel as it moves throughthe water in a submerged status. The devices are all relatively simple.and have relatively few moving parts so that there is little likelihoodof malfunction during their use. All are capable of being actuated andretrieved from the towing vessel and do not depend in any way uponactuating mechanism or electrical circuitry which must be located upon.or extended to, the tow.

Although several embodiments of the invention have een hereinbeforedescribed in detail so as to atford examples of the invention and themanner of its practice sullicient to permit those skilled in the art tobenefit from the practice of the invention, it is to be understood thatvarious modifications and innovations may be made in the describedstructures and procedures without departing from the basic principleswhich underlie the invention. Insofar, therefore, as changes andmodifications to the herein described method and apparatus continue torely upon and utilize the basic principles which have been disclosed anddescribed. such changes and modifica tions are deemed to becircumscribed by the spirit and scope of the present invention except asthe same may be necessarily limited by the appended claims or reasonableequivalents thereof.

I claim:

1. A device for decelerating a submerged vessel towedby a vessel'ohth es urface by mziirs'ara fiiib'le tow line,

said devic'ec'omprisingz ....ths-

9 t 2. A device as claimed in claim 1 wherein said control meanscomprises an elongated flexible member secured at one of its ends tosaid fluid flow resistance means and of a length to extend from saidresistance means to the towing vessel.

3. A device as claimed in claim 1 wherein saidhydrodynamic resistanceelement comprises a plurality of rigid resistance fins extendingradially outwardly from said annular body.

4. A device as claimed in claim 1 wherein said hydrodynamic resistanceelement comprises a plurality of elongated flexible members eachattached at one of its ends to said annular body'and each having acup-shaped, turbulence generating element attached to the other endthereof.

5. A device as defined in claim 1 wherein said hydrodynamic resistanceelement comprises a propeller mounted on said annular body and extendingradially outwardly therefrom whereby said propeller is caused to spinabout the axis of said annular body by the flow of water past thepropeller.

6. A device as claimed in claim 1 and further characterized to includebearing elements mounted in said annular body and projecting radiallyinwardly therefrom for contact with said tow line whereby said annularbody can move more easily along said tow line.

7. A device as claimed in claim 2 wherein said elongated flexible memberis a return cable and said control means is further characterized toinclude winch means adapted for securement to said towing vessel and connected to the other end of said return cable for reeling in and payingout said return cable.

8. A device for decelerating a submerged vessel towed by a vessel on thesurface by means of a flexible tow line, said device comprising:

' fluid fiow resistance means adapted for movement on said tow linebetween said submerged vessel and the towing vessel, and including:

an annular body dimensioned to slidably encircle said tow line forsliding movement therealong;

shock absorbing means secured to said annular body and disposed to oneside of said annular body along the axis thereof;

a hydrodynamic resistance element extending outwardly from said annularbody in a direction which is generally away from the axis of saidannular body; and

control means connected to said fluid fiow resistance means anddimensioned to extend at least from said resistance means to said towingvessel whereby the movements of said resistance means on said tow linecan be controlled from said towing vessel.

'9. A device for decelerating a submerged vessel towed by a vessel onthe surface by means of a flexible tow line, said device comprising:

fluid flow resistance means adapted. for movement on said tow linebetween said submerged vessel and the towing vessel, and including:

an annular body dimensioned to slidably encircle said tow line forsliding movement therealong;

a hydrodynamic resistance element extending outwardly from said annularbody in a direction which is generally away from the axis of saidannular body, said hydrodynamic resistance element comprising:

a plurality of rigid resistance fins extending radially outwardly fromsaid annular body;

a fin collar slideably mounted'on said annular body and pivotallyconnected to one end of each of said resistance fins; and

actuating means for pivoting said resistance fins between said radiallyoutwardly extending position and a position in which said fins extend atangle of less than 45 to the axis of said annular body; and

control means connected to said fluid flow resistance means anddimensioned to extend at least from said resistance means to said towingvessel whereby the movements of said resistance means on said tow linecan be controlled from said tow vessel.

10. A device for decelerating a submerged vessel towed by a vessel onthe surface by means of a flexible tow line, said device comprising:

fluid flow resistance means adapted for movement on towingvessel, andincluding:

an annular body dimensioned to slide'nbly encircle said tow line forsliding movement therealong:

a hydrodynamic resistance element extending out wardly from said annularbody in a direction which is generally away from the axis of saidannular body, said hydrodynamic resistance element comprising:

a plurality of rigidjresistance fins extending radially outwardly fromand pivotally mounted on said annular body; and

actuating means for pivoting said resistance fins inwardly toward saidannular body from and radially outwardly extending position; and controlmeans connected to said fluid flow resistance means and dimensioned toextend at least. from said resistance means to said towing vesselwhereby the movements of said resistance means on said tow line can becontrolled from said towing vessel.

11. A device as defined in claim 9 wherein said actuating means includesa retrieving ring slidably surrounding said annular body and spacedtherealong from said fin collar; and

braces extending from each of said fins to said retrieving ring and eachpivotally connected at one of its ends to one of said fins at a pointintermediate the length of the respective fin and pivotally connected atits other end to said retrieving ring.

12. A device as claimed 'in claim 11 and further characterized toinclude a flexible member interconnecting each of said resistance finsto the next adjacent resistance fins at points adjacent the radiallyouter ends of the interconnected resistance fins.

13. Apparatus for the marine transport of a liquid cargo comprising:

a towing vessel;

a submersible tow adapted to be towed under the water by said towingvessel;

a flexible tow line interconnecting the vessel and tow;

hydrodvnamicall actuatedadecelerating means mov- .ably mounted on saidtow line for movement theli' along between said towing vessel and tow;

shock absorbing means positioned between said decelerating means andsaid tow for cushioning the impact between said decelerating means andthe tow; and

c 9ntrol means extending from said decelerating means to said vessel forcontrolling the movementof characterized to include automatic tensioningmeans on saidvessel for automatically maintaining a predeterminedconnected to said deceler:

with on said tow line.

17. An apparatus as defined in claim 13 wherein said shock absorbingmeans includes a shock absorbing device positioned around said tow lineadjacent its end secured to the tow.

said tow line between said submerged vessel and the l 1 18. Apparatus asdefined in clain 13'wherein said decelerating means.-comprises a. sleeveslidably surrounding said tow line; and turbulence generating, fluidflow resistance means connected to said sleeve and extending outwardlythere from in a direction away from the axis of said sleeve. 19.Apparatus as defined in claim 18 wherein said turbulence generating.fluid flow resistance means includes at least one hydrostaticallyactuated movable element attached to said sleeve for movement relativethereto in response to relative movement between the sleeve and thewater when the sleeve is in contact with the water.

20. Apparatus as defined in claim 19 wherein said hydrostaticallymovable element is a propeller rotatably mounted on said sleeve forrotation about the axis thereof. 21. Apparatus as defined in claim 19wherein said hydrostatically movable element comprises a drogue; and

generating device so that said turbulence generating device andsubmerged vessel move relatively closer to each other until they contacteach other;

dissipating a portion of the energy released upon contact between saidsubmerged vessel and said turbulence generating device in a shockabsorber; and

after deceleration of the submerged vessel to the exlaQifiis moved pastthe turbulence generating device in part a flexible member connectingsaid drogue to said sleeve.

22. Apparatus as defined in claim 19 wherein there are a plurality ofsaid hydrostatically movable elements and said elements each comprise anelongated resistance fin pivotally mounted on said sleeve and movable ina plane containing the axis of said sleeve.

23. The method of decelerating the forward movement of a submergedvesselconnected by a tow line to a towing vessel comprising:

moving on the tow line from a position on the tow line above the waterand adjacent the towing vessel to a position in the water and closer tothe submerged vessel, a turbulence generating device which offersgreater resistance to the fiow of water thereby than does the submergedvessel;

moving the towing vessel away from the turbulence generating device andsimultaneously moving the tow line after the towing vessel and past theturbulence by the forward motion of said towing vessel and in part byreeling in said tow line on the towing vessel.

- References Cited by the Examiner UNITED STATES PATENTS 346,689 8/1886Schoening 114-209 X 2,359,366 10/1944 Katcher et al 114-235 3,039,4196/1962 Rimar l14-209 3,074,321 1/1963 Draim et al. 1l4--235 X ReferencesCited by the Applicant UNITED STATES PATENTS 637,142 ll/l899 Miller.2,491,564 12/1949 Ivcrsen.

3,047,259 7/ 1962 Tatnall et 8-].

3,086,490 4/1963 Nichols.

MILTON BUCHLER, Primary Examiner.

T. M. BLIX, Assistant Examiner.

1. A DEVICE FOR DECELERATING A SUBMERGED VESSEL TOWED BY A VESSEL ON THESURFACE BY MEANS OF A FLEXIBLE TOW LINE, SAID DEVICE COMPRISING: FLUIDFLOW RESISTANCE MEANS ADAPTED FOR MOVEMENT ON SAID TOW LINE BETWEEN SAIDSUBMERGED VESSEL AND THE TOWING VESSEL, AND INCLUDING AN ANNULAR BODYDIMENSIONED TO SLIDABLY ENCIRCLE SAID TOW LINE FOR SLIDING MOVEMENTTHEREALONG, AND A HYDRODYNAMIC RESISTANCE ELEMENT MOUNTED ON AND MOVABLERELATIVE TO SAID ANNULAR BODY; AND CONTROL MEANS CONNECTED TO SAID FLUIDFLOW RESISTANCE MEANS AND DIMENSIONED TO EXTEND AT LEAST FROM SAIDRESISTANCE MEANS TO SAID TOWING VESSEL WHEREBY THE MOVEMENTS OF SAIDRESISTANCE MEANS ON SAID TOW LINE CAN BE CONTROLLED FROM SAID TOWINGVESSEL.